Arrangement for color coding of surfaces

ABSTRACT

An arrangement in which different surfaces of an object have applied to them transparent layers of different colors. Each layer will transmit one or more colors, while inhibiting the transmission of one or more other colors. By applying different color layers or paints, so that the combination of layers have different transmission characteristics, different surfaces of an object may be uniquely identified. To identify a predetermined surface, the colors applied thereon are noted, and the surface is illuminated. A filtering arrangement used in conjunction with either the illuminating source or a photograph camera, causes unique exposure of the film, for a predetermined combination of color filter and color paints applied in sequence on the surface being examined.

BACKGROUND OF THE INVENTION

In the manufacture or production of articles, it is often desirable tobe able to identify different surfaces of the article for purposes ofapplying different production processes thereto. For example, an articlemay have different surfaces requiring different machining tolerances,and different machining procedures or tools. Color coding of surfaces isalso particularly useful when analyzing surfaces to obtain theirgeometrical characteristics. In such cases, a surface may be subdividedinto parallel, horizontal or vertical planes, for example, and eachplanar section thus generated on this surface by such subdivisionthereof, can be conveniently identified by a color coding process.

When mass-producing parts or articles in manufacture by automaticequipment, it is furthermore useful to color code different surfaceswhereby the different machine tools or production equipment may beactivated and applied when a predetermined surface of the part orarticle is exposed preparatory for a predetermined manufacturing step.

It is therefore an object of the present invention to provide a colorcoding arrangement for surfaces, which will result in uniquelyidentifying a surface as a result of predetermined colors appliedthereto.

Another object of the present invention is to provide an arrangement ofthe foregoing character which is substantially simple in constructionand may be applied without the use of complex equipment.

A further object of the present invention is to provide a color codingarrangement, as described, which may be economically produced andpracticed.

SUMMARY OF THE INVENTION

The objects of the present invention are achieved by applying todifferent surfaces of an object, different combinations of transparentlayers of colors. The surfaces are then illuminated by a source of whitelight, for example, and photographed by a camera in the presence ofselective filters placed either between the source of light and theobject, or between the camera and the object. By noting which colorfilter is being used in combination with the surface being photographed,a series of film exposures resulting with different filters, may be usedto identify uniquely the surface being thus photographed.

The camera may be a black-white camera used in conjunction with a sourceof illumination and color filters, or the camera may be a color cameraused in conjunction with a white source of light, for example.

To identify a color-coded surface, the sequence of photograph framestaken with the camera, are scanned to determine which frame has beenexposed in conjunction with a predetermined filter that was used forthat particular exposure.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view and shows the essential elements and theircooperative interrelationships, in accordance with the presentinvention; and

FIG. 2 is a schematic view and shows an arrangement used in conjunctionwith FIG. 1 when applying color photograph.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, an object 10 has different surfaces 12-14,for example, which are to be treated differently in a productionprocess. Such different surface treatments may consist of, for example,applying different milling cutters or different cutting surfaces of amilling cutter to the different surfaces on the object 10, for thepurpose of forming that surface. The contour of the surface section 12,for example, may require a predetermined milling cutter withpredetermined cutting surface profile, which is different from therequired milling cutter for the neighboring surface element 13.Alternately, the same milling cutter to be used throughout, may berequired to have a different orientation so as to expose a differentcutting profile for each of the different surface segments 12-14. Toapply the desired tool in such an arrangement, therefore, it isnecessary to identify the different surface sections 12-14. For the sakeof maintaining the description simplified, reference numerals 12-14 havebeen applied to only 3 surface sections of the object 10, whereas thelatter may be subdivided, of course, into numerous additional sections.

For purposes of identifying uniquely each of the different surfacesections on the object 10, each section is painted with a series ofdifferent colors applied in layers or coats by the color applying means11. To understand how such application of layers of paints may be usedfor such identification purposes, it may be helpful to consider anopaque white paint or ink. The base is a liquid "vehicle," usuallylinseed oil. The vehicle is quite colorless and transparent. Suspendedin it are tiny particles of equally colorless and transparent material,such as an oxide of lead, zinc, or titanium. The index of refraction ofthe suspended material must be as different as possible from that of thevehicle. When a ray of light strikes the surface of the white paint,some light will be reflected at the air-vehicle surface, since there isa change in index at this surface. The remainder penetrates into thepaint and strikes a boundary between vehicle and suspended particle,where again a portion is reflected. The reflected part returns throughthe surface, and the part remaining penetrates further, a portion beingreflected at each boundary surface which it crosses. Since reflectionoccurs whatever the wavelength of the incident light, the paint reflectsuniformly throughout the spectrum, or in other words, it is "white". Thewhite "color" is not produced by suspending white particles in thevehicle. It is due to a difference in index between particle andvehicle, both of which are transparent.

If a colored paint or ink is desired, the suspended particles are dyedthe desired color, or other dyed particles are added to the white paint.The dyed particles then behave as tiny filters in the path of the lightrays in the paint. The light reflected back out of the paint must passthrough many of these filters on its way in and out, each filterabsorbing some of the light incident upon it. The spectral distributionof the incident light is modified by this absorption, and results incoloring the paint. The same spectral distribution will be obtainedwithout reflecting particles being present in the paint if a whitereflecting surface is located beneath the coat containing the dyedparticles.

When blue and yellow layers of paint are applied to a surface, forexample, then the light rays will pass through both the blue and yellowfilters before making their way out of the surfaces of the layers. Theeffect is substantially the same as produced when a blue and yellowfilter are placed in series in the path of a light beam. If the layersobtained are illuminated by white light, then green will predominate inthe reflected light, and the resulting color that will be noted fromsuch blue and yellow layers is green. The occurs because the blue paintfilters out red and the yellow paint filters out blue. Hence only greenemerges from both layers.

The particular portion of the spectrum that each dye or paint controls,is that portion in which it absorbs. The greater the density orconcentration, the more light is absorbed; the smaller itsconcentration, the less light is absorbed. Such absorbancecharacteristics may be attributed to three different dyes designated,for example, as "minus-red," "minus-green" and "minus-blue." The colorof the "minus-red" dye or paint, when applied to a white surface andviewed by white light, is blue. The color of the "minus-green" is areddish purple or magenta. The color of the "minus-blue" is yellow.

If, now, three colors are used in a digital combination of presence orabsence, seven surfaces may be identified since 2³ -1=7. This may beseen by considering the following tabular arrangement of three colors,1, 2, 3 which may be used for example. In this table, the presence ofany one of the three colors is denoted by an (x). It may be seen fromthis, that seven different arrangements (a) to (g) may be obtained.

    ______________________________________                                        PRESENCE OF COLORS                                                            1            2         3                                                      ______________________________________                                        x            X         x          (a)                                         x            x                    (b)                                                      x         x          (c)                                         x                      x          (d)                                         x                                 (e)                                                      x                    (f)                                                                x          (g)                                         ______________________________________                                    

If several states are assigned to each color, more digital combinationsare obtainable. For example, if at least one color is used at fullintensity (substantially unattenuated) for every painted region, thefollowing number of combinations result: 3³ -2³ -1=18. Thus, each colorhas three allowable states in the form of full intensity, partialintensity or zero intensity. From this one might expect 3³ states.However, in 2³ states there is no full intensity color, and in one stateall colors are zero. The full intensity state is necessary to providefor a basis of comparison in the intensity levels.

The object 10 with different surface sections or regions 12-14, forexample, may be located on a support 16 and illuminated by a source 18of white light. A camera 20 is placed in the path of reflected lightfrom the object 10. A filter unit 22 may be located in the light pathbetween the source 18 and the object 10.

If the object 10 is illuminated with white light and photographedsequentially with different color filters, a series of photographs willbe obtained with different exposure characteristics. By knowing whichcolor filter was used with an exposure or photograph, it is possible todetermine the color that was photographed and it is thereby possible toidentify the surface bearing that color.

In applying the present invention to a manufacturing operation, forexample, the photograph 24 taken by the camera 20 may be examined orscanned by a scanner and comparator 26. The scanner views the photograph24, which is a black-white photograph taken by a black-white camera 20.The scanner 26 determines whether the photograph 24 has been exposed ornot at each particular location on the photograph. The output of thescanner 26 may be applied to a computer 28. Connected to the computer28, is also the signal output of a transducer 30 which transmits adigital signal, for example, indicating which color filter is beingused. For this purpose, different colored filters 23, when being used,have different associated rotational positions of the wheel 22. Thetransducer 30 connected to the wheel 22 senses the rotational postion ofthe wheel, and transmits a signal, in digital form to the computer 28.Elements such as transducer 30 are well known in the art, and are oftenreferred to as shaft encoders. For this reason, this element is notdescribed in further detail here.

The computer correlates the exposure information from the scanner 26with the particular color filter being used at the time that theexposure was taken, and provides a calculated output which identifiesthe color of the surface that was photographed. Identification of thecolor results in identification of the given surface to which the colorhas been applied.

The exposure or non-exposure of the film may be detected by the scanner26 and transmitted to the computer 28 by means of a digital signal inthe form of, for example, 0,1. At the same time, however, the signalstransmitted to the computer 28 may also be in analog form, usingconventional analog signal transmission techniques. The color paints ordyes may be arranged so that the film in the camera 20 may be exposed byeither the presence of a predetermined color or the absence thereof.Either information can be correlated by the computer 28.

It is not essential that the filter unit 22 be located within the lightpath between the source 18 and the object 10. It is possible to useinstead, or in addition thereto, another filter unit 31 within the lightpath between the object 10 and the camera 20. When convenient, forexample, the additional or auxiliary filter unit 31 may be positionedwithin the light path or removed therefrom.

When using a color camera in the place of a black-white camera, it isnot necessary to use filter units. In that event, the photographs takenby the camera are color photographs, and these may be analyzed as shownin FIG. 2, by illuminating the color photograph 32 by a source of whitelight 34. A scanner 36 used in conjunction with a filter unit 38, canidentify the color on the photograph by sensing the presence or absenceof transmitted light through the filter, and correlating the informationwith the particular filter being used in a computer, as previouslydescribed. The filter unit 38 in this arrangement, is similar to thefilter unit 22, and operates in conjunction with a transducer 40 whichis also substantially identical to the unit 30.

The camera used in the present invention, may also be in the form of ablack-white or color television camera. In such cases, the scanner 26would view the screens of a corresponding black-white or colortelevision receiver instead of photographic prints, for example.Alternatively the video output from the TV camera may be decodedaccording to color and intensity, and this information may be sent tothe computer. The use of television apparatus, for this purpose, isparticularly advantageous in continuous-flow manufacturing processes, inwhich parts or articles are fabricated on a continuous basis.

In manufacturing processes, it is often required to subject thefabricated articles or parts to inspection procedures, wherein theshape, size or smoothness of the object are compared to a standard. Thefabricated part or object may often possess numerous features, each ofwhich may be associated with different tolerance bands. The presentinvention provides for a rapid comparison system in which individualsurfaces or features of the object may be identified and measurementsmay be correspondingly applied for comparison to determine whether thefabricated parts are within the allowable manufacturing tolerances. Thisis of particular importance during processes using three-dimensionalinformation sensing techniques such as disclosed in U.S. Pat. No.3,866,052.

For purposes of color coding the different surfaces of the object, aseparate color paint may be applied to each surface region to beidentifed, or different combinations of coats or layers of transparentpaints may be applied.

In lieu of the white source of light and a separate filtering unit 22,the source of colored light may be used. Such an arrangement may beconsidered as having the filter built into the light source. Denoting orrecording of the particular colored light being used, for processing bythe computer 28, is the same as in the arrangement described previously.

In taking multiple photographs by the camera, the relative light valuesthat are observed, provide the basis for identifying the color on eithera digital or analog basis. The relative light values to be observed maybe in the form of film density, television signal, or photocell outputs.

Whereas the source of illumination may be white light or colored light,electromagnetic radiation of other frequencies may also be used, as forexample, infrared.

The color coding arrangement used in accordance with the presentinvention has also the advantageous feature that the number ofphotographs taken can be considerably less than the number of surfacesto be identified. Thus by taking three photographs with three differentfilters, for example, seven different surfaces may be identified. Thisfeature is of particular importance in the aforementioned U.S. Pat. No.3,866,052 which discloses a method for generating signals definingthree-dimensional object surfaces. For purposes of defining the locationof an object surface point in space, the surface is subdivided into aplurality of planar segments which are encoded. The planar segments orbands may be encoded using a pure binary code, decimal-binary codes, orternary codes, for example. In such an arrangement, the object 10 issubdivided into parallel surface sections such as shown in FIG. 1. Acolor scheme can be applied advantageously, in accordance with thepresent invention, for purposes of identifying the parallel planarsurface sections. In such a color scheme, three distinct colors as, forexample, red, green and blue may be used.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention,and therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed is:
 1. A method for color coding surfaces of an objectcomprising the steps of: applying at least one color to a surface of theobject; illuminating said surface with electromagnetic radiation;modifying said electromagnetic radiation in accordance with apredetermined color dependent function; observing at least onecharacteristic in electromagnetic radiation reflected from said surface;combining a predetermined number of colors in a digital combination ofpresence and absence to identify uniquely each of a plurality ofsurfaces; said color applying step including applying said color withlayers of transparent paint having a colorless vehicle with coloredparticles suspended therein, said particles having an index ofrefraction differing from the index of refraction of the vehicle, saidparticles forming filters in paths of light rays in the paint, incidentlight reflected back out of the paint passing through said filters whenentering and exiting and each filter absorbing some light incident uponit, the spectral distribution of incident light being modified by theabsorption of coloring the paint; said illuminating step comprisingilluminating the surfaces during a plurality of separate intervals withcolored light; the light color during each interval being different fromthe light colors illuminating said surfaces during other intervals; saidobserving step including photographing said surfaces during each saidinterval; scanning each photograph in sequence and sensing saidcharacteristic in reflections from said surfaces; and correlating saidcharacteristic with said color dependent function for identifying thecolor applied to said surface; said correlating step including the stepof relating the number of surfaces to the number of photographs by adigital code so that the number of photographs taken is substantiallyless than the number of surfaces to be identified.
 2. A method asdefined in claim 1 including the step of introducing a color filter inthe path of said electromagnetic radiation for modifying saidelectromagnetic radiation in accordance with said predetermined colordependent function.
 3. A method as defined in claim 1 wherein saidobserving step includes applying reflections from said surface to atelevision camera.
 4. A method as defined in claim 1 wherein saidphotographing steps are carried out with a color camera.
 5. A method asdefined in claim 3 wherein said television camera is a color camera. 6.A method as defined in claim 1 wherein said photographing steps arecarried out with a black-white camera.
 7. A method as defined in claim 3wherein said television camera is a black-white camera.
 8. A method asdefined in claim 1 wherein said correlating step is carried out within acomputer.
 9. A method as defined in claim 3 including the step ofscanning signals transmitted from said television camera for sensingsaid characteristic in reflections from said surface.
 10. Apparatus forcolor coding surfaces of an object comprising, in combination: means forapplying at least one color to a surface of the object; means forilluminating said surface with electromagnetic radiation; means formodifying said electromagnetic radiation in accordance with apredetermined color dependent function; means for observing at least onecharacteristic in reflections from said surface; said color applyingmeans applying said color with layers of transparent paint having acolorless vehicle with colored particles suspended therein, saidparticles having an index of refraction differing from the index ofrefraction of the vehicle, said particles forming filters in paths oflight rays in the paint, incident light reflected back out of the paintpassing through said filters when entering and exiting and each filterabsorbing some light incident upon it, the spectral distribution ofincident light being modified by the absorption for coloring a paint;the predetermined number of colors being combined in a digitalcombination of presence and absence to identify uniquely each of aplurality of surfaces; said illuminating means illuminating the surfacesduring a plurality of separate intervals with colored light, the lightcolor during each interval being different from the light colorsilluminating said surfaces during other intervals; said observing meansphotographing said surfaces during each said interval; means forscanning each photograph in sequence and sensing said characteristic inreflections from said surfaces; and means for correlating saidcharacteristic with said color dependent function for identifying thecolor applied to said surface, said correlating means relating thenumber of surfaces to the number of photographs by a digital code sothat the number of photographs taken is substantially less than thenumber of surfaces to be identified.